A thirty-six-year-old female brittle diabetic presented in a confused state complaining of intense thirst. She had a twelve-year history of known diabetes mellitus but for the previous five years had been well controlled. Four years before admission she was found to be euthyroid with a PBI of 6.8 meg. per 100 ml.
On examination she was dehydrated and without Kussmaul respirations. Blood sugar on admission was 1,590 mg./100 ml. and only a trace of acetone was detected in urine. Calculated serum osmolality was 365 milliosmols/liter. The patient responded well to 800 U. of Regular Insulin and eight liters of intravenous hypotonie solutions. However the pulse rate remained at 140/min. with no evidence of heart failure or infection; EKG showed sinus tachycardia. Evaluation of the patient's thyroid function revealed hyperthyroidism. I-131 uptake after twenty-four hours was 74 per cent. The glucocorticosteroids were found to be within normal limits.
Four months after receiving methimazole 40 mg./day the hyperthyroidism and diabetes mellitus were well controlled.